With emergence of data centers and big data applications, large-capacity and short-distance interconnection becomes an important application scenario. This application addresses a new requirement for a system, particularly for lower device costs, a longer transmission distance, and a larger transmission capacity.
An existing high-speed optical signal transmitter may use a plurality of optical devices, for example, an external light source, a beam splitter, and a beam combiner, to generate a single sideband (SSB) modulation symbol, a multi-level pulse-amplitude modulation (PAM) signal, a multi-symbol quadrature amplitude modulation (QAM) signal, and the like. For example, in a conventional implementation, an SSB signal or a multi-level QAM signal may be generated by passing an external light source through a beam splitter, two modulators, a phase control area, an optical synthesizer, and the like. This implementation requires an integrated in-phase quadrature (IQ) modulator to modulate a phase and the like. For another example, in a conventional implementation, a non-return-to-zero (NRZ) code modulation signal or a multi-level PAM signal may be generated by using an electro-absorption modulated laser (EMI), a directly modulated laser (DML), or the like. However, the multi-level PAM signal has a relatively high linearity requirement for a device. In these conventional methods, the use of an IQ modulator or a growing linearity requirement for a device addresses a relatively high requirement for the device, and costs of the entire device are relatively high.